Unless you really need to get a certain time, I'd definitely recommend running both races for fun. There aren't many races around that offer the amount and variety of on-course entertainment that Disney does, so you might as well take advantage of it while you can. Stop for photos with the characters, take in the sights and sounds around you, and make the most of the morning. I've done this for all of my Goofy and Dopey races except one where I absolutely had to run a specific time as a qualifier for another event. It wasn't a ton of fun to have to pass by all the characters, spectators, WISH cheerleaders, etc., without having an opportunity to stop and soak it all in. And if you do decide to run for fun, try to run slowly enough, or stop enough to make your time longer, that you can stop and ride the coaster in Animal Kingdom.